1. Field of the Invention
The present invention concerns a method of milling at least a localized region such as a key or lug or a groove on a workpiece.
2. Description of the Prior Art
Conventional methods of machining such workpieces comprise two successive operations:
1-Turning portions which are bodies of revolution, leaving unmachined the portions that are to have a straight axial profile such as lugs or keys. PA1 2-Further machining of the workpiece to form the straight shapes. This further machining is done on a press, which has the major drawback of deformation of the workpiece, or on a nibbler, which has the drawback of long machining times, or on a milling machine, which has the drawbacks of a long machining time on a high-cost machine. PA1 rotating the workpiece about a horizontal axis of a cylindrical region thereof, said cylindrical region having a radius R.sub.p, PA1 bringing an external contour of radius R.sub.F of a tool into contact with said cylindrical region of said workpiece at a machining point, PA1 said tool rotating about a rotation axis intersecting a first transverse axis of said workpiece perpendicular to said longitudinal axis and intersecting the latter, said rotation axis being in a plane parallel to said longitudinal axis and to a second transverse axis of said workpiece perpendicular to said first transverse axis and to said longitudinal axis and intersecting them, the rotation axis being at an angle .alpha. to said second transverse axis.
Techniques known collectively as "polygonal turning" are used to make parts with a regular polygonal cross-section (flats, for example). These techniques are described in patent applications FR-A-2 301 326 and FR-A-2 171 187, for example.
These techniques are based on an operation combining milling and turning using a milling machine having a rotation axis parallel to the axis of the workpiece, an angular rotation speed synchronized to that of the workpiece and the same rotation direction as the workpiece so that at the point of contact of the workpiece and the tool the respective peripheral speeds are in opposite directions. This latter technique is described in "Dispositif de filetage par fraise et de tournage polygonal TD" (April 1974-Hemmann TRAUB MACHINEFABRIK-West Germany). It is not suitable for making keys or lugs.
An object of the present invention is a method of milling for forming localized regions such as keys or lugs in a single operation, in less time and therefore at reduced cost.